Cree Sammie

I had a spare BB400 lying around and some McR16's and 17's so I decided to try making a Cree Sandwich. It was a very worthwhile effort. The BB400 with the P4 Cree easily outshines a BB400 with an SWOH. To keep the Cree from shorting out through the bottom pads, you must grind off the corners of the ceramic. Do it carefully and you will eventually expose the via which connects the bottom pads.

Here it is in a M@g 2AA host





Some shots of the sandwich






Obligatory white wall shot. Cree on left, SWOH on the right. Both LED's driven with BB400's




The red nail polish is for added insulation against shorts against the body. This turned out to be unnecessary in the end though if you're careful about your build.



Enjoy.

Nice mod Cris. Real life output should be around 60 lumens, and relatively cool. Will be pretty easy on NiMh's.

Bill

Bullzeyebill said:

Nice mod Cris. Real life output should be around 60 lumens, and relatively cool. Will be pretty easy on NiMh's.

Bill

Click to expand...

The SWOH actually doesn't draw that much more current than the Cree but I have to admit that I handpicked the SWOH for lowest Vf when I built it while the Cree was a grab-bag. Bouncing the light off the ceiling, a lightmeter indicates that the Cree puts out 1.7x more light overall than the S bin Lux I. In retrospect, I probably should have biased the Cree much lower, about 250mA or so, and I would get the long runtime while giving the same output as the S bin sammie. Current draw from 2xNiMH is 630mA. 5 hour runtime with reduced drive is sounding like a mighty tasty sandwich :naughty:

That's some nice clean work. Great job!

Nice mod...
I'm curious, how high is the sammie ?

Thanks guys. I actually think this is a little sloppy since I was so anxious to put it together that I made no effort to give it the "polished" appearance.

bombelman, the sammie is the same height as standard sammies from the shop. I just eyeball it, I didn't make measurements. Just like the way I cook

Got to thinking about 250mA's to Cree, and remembered that you had replaced my Arc LSH stock led with a SWOH with bias set to 250mA's. I had reported to you that using a used Streamlight CR123 starting at 3.15 volts I got a flat runtime of 4 hours and 3 minutes (lightmeter and bounce). Later I did a run with two Costco Alkalines and got 3 hours and 5 minutes. Use of nimh's would have resulted in a longer runtime in regulation.

A Cree Sammie at 250mA's to led with a fairly low vf, would be outstanding runtime wise and lumen wise, even using plain wrap alkalines.

Bill

I've been thinking of building one of these. Do you think a McR 19XR would fit in a minimag head, or is it too long?

Bill, that Arc was exactly what I was thinking

Gnufish, the McR19 is too long. I'm trying to come up with a workaround sammie which will also apply to using the McR16's in the Firefly.

Let me know if you come up with a workaround, otherwise I'll go with the 17XR.

How is the reflector attached to the head? Is if focusable (de-focusable)?

I'll post my workaround results. The McR16 actually works better due to slightly shorter length. The reflector floats right now but can probably be retained using a thick O-ring. It is not focusable and even if it was, the range of adjustment would not be wide anyways.

Neat solder job. I'm in the process of making a Cree sammie as well, it works but I have some awfully ugly blobs of solder on mine. If you don't mind my asking, what gauge wire are you using?

PhotonAddict said:

Neat solder job. I'm in the process of making a Cree sammie as well, it works but I have some awfully ugly blobs of solder on mine. If you don't mind my asking, what gauge wire are you using?

Click to expand...

Thanks. Soldering is a skill. The more you do, the better you get. Having a good soldering iron is essential. Clean all areas that the solder has to adhere to and use flux (but use it sparingly) I use 22 guage stranded wire and then removed a few strands. Heat the joint to cause the solder to flow to the joint. Do not melt the solder to cause it to flow to the joint (though you probably knew that already

CM said:

Heat the joint to cause the solder to flow to the joint. Do not melt the solder to cause it to flow to the joint (though you probably knew that already

Click to expand...

:thinking:

i THINK IT MEANS TO PUT THE HEAT TO WHERE THE SOLDER NEEDS TO FLOW TO, RATHER THAN APPLY THE SOLDER TO THE IRON FIRST, AS THIS BURNS OFF FLUX AND CREATES IMPERFECT HEAT TRANSFER.

Can create bad solder joins if the heat hasn't transferred properly.

Sorry for the caps - I ain't re-typing it! lol

Pila_Power said:

i THINK IT MEANS TO PUT THE HEAT TO WHERE THE SOLDER NEEDS TO FLOW TO, RATHER THAN APPLY THE SOLDER TO THE IRON FIRST, AS THIS BURNS OFF FLUX AND CREATES IMPERFECT HEAT TRANSFER.

Can create bad solder joins if the heat hasn't transferred properly.

Sorry for the caps - I ain't re-typing it! lol

Click to expand...

What he said

CM said:

Heat the joint to cause the solder to flow to the joint. Do not melt the solder to cause it to flow to the joint (though you probably knew that already

Click to expand...

True, I've used to consider myself reasonably good at soldering until I started playing with these little guys. When heating the joint I'm always afraid of applying too much heat and damaging the led (or the smt in my last project). The contacts on the Cree seemed to require more heat than I expected.
Like you said, I probably just need to more practice. Hmm, I guess that means more mods/lights

CM,
Sorry for being a bit OT, but I would like to ask you how the beam profile of the Cree/McR16 is compared to a stock L5. I'm particularly pleased with the large hotspot and soft blend into sidespill of the L5. Is this combo anything like that, or is it a sharper transition from hotspot to spill and a smaller hotspot?

Thanks
Jan

Very nice!! I tried once but it doesn't look this good. :goodjob:

JanCPF said:

CM,
Sorry for being a bit OT, but I would like to ask you how the beam profile of the Cree/McR16 is compared to a stock L5. I'm particularly pleased with the large hotspot and soft blend into sidespill of the L5. Is this combo anything like that, or is it a sharper transition from hotspot to spill and a smaller hotspot?

Thanks
Jan

Click to expand...

The beam profile is actually closer to the old batwing than the lambertians. The hotspot is very large and sidespill is BIG. Transition from hotspot to spill is very smooth and not as sharp as say, an A19 Cree. But you give up nothing in throw compared to a similarly biased S-bin Lux I behind a 20mm IMS reflector. The total output of the Cree is high enough to overcome the fact that you get a lot more light in the spill area. I have used this mod for reading (though it probably needs to be biased down quite a bit from 416mA for that since it is too bright)